Here's a little blurb from SurplusRifle.com:
Okay…so it looked strange, but it looked INTRIGUING. So off to the World Wide Web I went.
Turns out that the FR-8 is exactly as I thought, a half 20th and half 19th century rifle (sort of). Back in the 1950’s, the Spanish government was working with CETME (Centro de Estudios Tecnicos de Materiales Especiales or center for the study of technical materials) to develop an assault rifle for its armies. German weapons designers working with CETME developed the so called CETME assault rifle, which was later to become the G3 rifle for the German army...
So, Spain was in the process of implementing the CETME assault rifle, but there were not enough of the new assault rifles around for issue and training. They did, however, have gobs of old Mauser bolt actions (1916 and 1943 models). They developed a rifle that not only could be used to arm non combatant and “Guardia Civil” troops, but also would fill the gap in training purposes until more CETME assault rifles were on line. Hence, the FR-7/FR-8 was born.
A more in-depth article here.
Thanks, MissSpeech! Love you!